The applicant has searched the commercial availability of filtered cold air return systems and conversely return air systems for air conditioning units which in effect are warm air returns. Applicant has found no such devices and it appears that the primary filtering system in either an air conditioned or heating facility relies on the filtering of the air being delivered rather than air being returned. Obviously the placement of a filter into this return system will provide an ease of access for changing of the filters and will increase the filtering effectiveness,
In a search of the prior patented art the applicant has found the following listed U.S. Pat. Nos.: Schroeder, No. 4,713,799, Dec. 15, 1987: Tynan, No. 1,429,811, Sep. 19, 1922; Tropicana, No. 3,046,719, Jul. 31, 1962; Altman, et al., No. 1,726,792, Sep. 3, 1929; Wright No. 1,694,089, Dec. 4, 1928; Anderson, No. 1,886,460 Nov. 8, 1932.
The Anderson and Wright patents are directed to floor type registers and are not directly associated with the register and therefore require total removal of the register for filter access. The Tynan reference is a register attachment and therefore is not integral with the duct system. The Schroeder unit specifically provides a plenum for positioning of a filter behind a hinged grill work and is primarily directed to an overhead air moving system. Applicant's device is particularly directed to a return duct either for retro-fit or new installation and is particularly designed for accommodating baseboard duct mounting. The applicant's design includes ease of access to the filter medium for removal and replacement thereof.
Obviously an advantage of applicant's unit is to increase filtering effect by adding to the normal single furnace or air conditioning filter which only filters upon introduction of air to the used area. By filtering return air the unit accommodating the air movement receives the air in a cleaner condition which is beneficial to the operating unit and probably most commonly is the ease of filter change. Although normally recommended maintenance is to change the primary filter on a regular basis, most homeowners forget to do so and the available placement of returned units in, for example, a home may alert the homeowner to the need for such change.
It is therefore an object of the applicant's invention to provide a filter structure for placement in combination with a return air duct of a forced air heating or cooling unit for filtering of the air as it begins its return cycle.
It is a further object of the applicant's invention to provide a filtered return air structure which provides for ease of access to the filter material for placement and replacement in the air flow line.
It is still a further object of the applicant's invention to provide a baseboard return air filter device for retrofit or new installation including a replaceable filter element therein.